Numerous attempts to prefabricate building units or to create buildings from modular units are known to have been undertaken. It has long been recognized that modular construction would be advantageous in situations where large numbers of relatively inexpensive three dimensional building units were needed and where such units be produced in a uniform manner. To that end, prefabricated portions of buildings such as trusses and wall sections are commonly employed. However, the inventor herein is unaware of any successful undertakings wherein a complete unit, including both interior walls and roof, have been cast, integrally in three dimensional monolithicly in concrete in a modular form that was both esthetically pleasing and commercially viable. U.S. Pat. No. 4,180,233 is the most advanced prior art reference known to the inventor and purports to solve the many problems associated with this type construction. The '233 patent noted that one problem with such constructions was the inability to disengage internal mold parts without forming the walls at an angle which was considered undesirable. Yet, '233 was unable to solve this dilemma, as is shown by FIG. 2 of the patent and the improvements shown in FIGS. 12-17. The improvements attempted to make the release of the inner mold components "automatic". It is submitted that the approach outlined therein is not workable inasmuch as positive action to remove the internal mold walls from the casting is required to successfully extract the casting from the mold. This is accomplished in the present invention in a manner which produces a superior casting in terms of its esthetic appearance and in terms of the reusability of the mold. That is to say, the prior art produced only fixed rectangular mold units which were not alterable and could not be reconfigured for further use. Thus, the cost of such units was prohibitive to amortize on a single project and there was no means to provide variation in building style.